subroutine collimator(x0,x1,y0,y1)

      implicit none

      include 'const.inc'

      double precision x0,x1,y0,y1

      if((x1.ge.(-0.1)).and.(x1.le.0.1)) then !center septum 2mm wide -KG
        x1 = -1.d6
        y1 = -1.d6

      endif

      if (x0*x1.lt.0) then
        x1 = -1.d6
	  y1 = -1.d6
	end if
   
      return
      end